Oil Leakage Detector and Oil Leakage Detection Method and Image Processing Unit

ABSTRACT

An oil leakage detector of the present invention includes an image processing unit wherein the image processing unit calculates the values of saturation and intensity of each pixel in the color image of the object after an ultra-violet light is irradiated thereon, draws an intensity-saturation characteristic line of the saturation expressed in an X-axis and the intensity expressed in a Y-axis, sets an upper limit and a lower limit of intensity of each saturation as a threshold value based on an area without oil adhesion on the surface of the object, and determines, in the intensity-saturation characteristic line, an area corresponding to a pixel group where the intensity exceeds the threshold value of the upper limit and a pixel group where the intensity falls below the threshold value of the lower limit, to be an oil leakage adhered area.

CLAIM OF PRIORITY

The present application is a continuation of U.S. application Ser. No.15/053,294 filed Feb. 25, 2016, which claims priority from JapanesePatent application no. 2015-053117, filed on Mar. 17, 2015, the contentsof which are hereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION (1) Field of the Invention

The present invention relates to an oil leakage detector and an oilleakage detection method, and particularly to an oil leakage detectorand an oil leakage detection method suitable for detection of an oilleakage in an oil-filled device such as a transformer, a condenser, ahydraulic operation device for GIS (gas insulated switchgear), arectifier or the like.

(2) Description of the Related Art

There has heretofore been a concern for an oil storage tank or atransformer or the like to cause a leakage of oil (oil leakage) due todeterioration or an accident or the like. Since the oil leakage may leadto environment pollution and disasters, there has been a demand for asimple and highly-accurate detection technology in an early stage of theoil leakage.

As a related art technology for addressing this problem, there are knownthose described in Patent Documents 1 and 2.

Japanese Patent Application Laid-Open Publication No. 2008-116389(Patent Document 1) describes that when ultra-violet light including anabsorption wavelength of leakage oil is irradiated on an object to bemeasured from outside, fluorescence emitted from the leakage oil isdetected, and that the accuracy of detection of fluorescence is enhancedby using a filter through which a visible light component ofultra-violet light (black light) does not pass, and a bandpass filterwhich allows the center wavelength of the fluorescence to passtherethrough.

Further, Japanese Patent Application Laid-Open Publication No.2013-101474 (Patent Document 2) describes that the presence or absenceof oil is determined based on the intensity of a predetermined specificcolor in colors at respective pixels of a color image of colored leakageoil.

In the technology described in Patent Document 1, however, the intensityof fluorescence which reaches a detector was reduced with the use of thebandpass filter. For example, it was difficult for the technology todetect a small amount of leakage oil adhered to the surface of atransformer. Further, the technology was accompanied by a problem thatthe structure of the detector was complicated when using an opticalfilter.

On the other hand, there has been a demand for the technology describedin Patent Document 2 to establish a detection technology which issimple, e.g., filterless, and capable of also detecting a leakage ofcolorless oil because it is not possible to detect the colorless leakageoil.

The present invention has been made in view of the foregoing. An objectof the present invention is to provide an oil leakage detector and anoil leakage detection method both high in detection accuracy, which arecapable of also detecting colorless oil without complicating the oilleakage detector.

SUMMARY OF THE INVENTION

In order to address the above problems, an oil leakage detector of thepresent invention is provided which includes an ultra-violet lightirradiated on an object to be measured, a color camera which photographsfluorescence from the object irradiated with the ultra-violet light, acontrol unit which controls operations of the ultra-violet light and thecolor camera, a recording unit which records an image of the objectphotographed by the color camera, an image processing unit which invokesthe image recorded in the recording unit to determine an oil leakage,and a display unit which displays a result of determination by the imageprocessing unit. The image processing unit calculates the values ofsaturation and intensity of each pixel in the color image photographedby the color camera and draws an intensity-saturation characteristicline of the saturation expressed in an X-axis and the intensityexpressed in a Y-axis, sets an upper limit and a lower limit ofintensity of each saturation as a threshold value based on an areawithout oil adhesion on the surface of the object, and determines, inthe intensity-saturation characteristic line, an area corresponding to apixel group where the intensity exceeds the threshold value of the upperlimit and a pixel group where the intensity falls below the thresholdvalue of the lower limit, to be an oil leakage adhered area.

Further, in order to address the above problems, an oil leakagedetection method of the present invention is provided which comprisesthe steps of, when an oil leakage adhered area of an object to bemeasured is detected by an oil leakage detector including anultra-violet light irradiated on the object, a color camera whichphotographs fluorescence from the object irradiated with theultra-violet light, a control unit which controls operations of theultra-violet light and the color camera, a recording unit which recordsan image of the object photographed by the color camera, an imageprocessing unit which invokes the image recorded in the recording unitto determine an oil leakage, and a display unit which displays a resultof determination by the image processing unit: calculating by the imageprocessing unit, the values of saturation and intensity of each pixel inthe color image photographed by the color camera for photographing thefluorescence from the object irradiated with the ultra-violet light;drawing an intensity-saturation characteristic line of the saturationexpressed in an X-axis and the intensity expressed in a Y-axis; settingan upper limit and a lower limit of intensity of each saturation as athreshold value based on an area without oil adhesion on the surface ofthe object; and determining, based on the intensity-saturationcharacteristic line, an area corresponding to a pixel group where theintensity exceeds the threshold value of the upper limit and a pixelgroup where the intensity falls below the threshold value of the lowerlimit, to be an oil leakage adhered area by the image processing unit.

According to the present invention, an oil leakage detection high indetection accuracy, which makes it possible to also detect colorlessoil, can be carried out without complicating a device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration view showing an embodiment 1 of anoil leakage detector of the present invention together with anintensity-saturation graph;

FIG. 2 is a side view showing an oil-filled transformer to which the oilleakage detector of the present invention is applied;

FIG. 3 is a plan view of FIG. 2;

FIG. 4 is a perspective view showing an object to be measured adopted inan embodiment 2 of the oil leakage detector of the present invention;

FIG. 5 is a flowchart for describing an oil leakage detecting operationin the embodiment 2 of the oil leakage detector of the presentinvention;

FIG. 6A is a schematic view showing an image photographed in theembodiment 2 of the oil leakage detector of the present invention;

FIG. 6B is a schematic view showing the image processed in theembodiment 2 of the oil leakage detector of the present invention;

FIG. 7 is a perspective view showing an object to be measured adopted inan embodiment 3 of the oil leakage detector of the present invention;

FIG. 8 is a flowchart for describing an oil leakage detecting operationin the embodiment 3 of the oil leakage detector of the presentinvention;

FIG. 9 is a flowchart for describing an oil leakage detecting operationin an embodiment 4 of the oil leakage detector of the present invention;

FIG. 10 is a view showing an intensity-saturation relationship of an oilleakage detection method in an embodiment 5 of the oil leakage detectorof the present invention;

FIG. 11 is a flowchart for describing an oil leakage detecting operationin an embodiment 6 of the oil leakage detector of the present invention;

FIG. 12 is a view showing an intensity-saturation relationship of an oilleakage detection method in the embodiment 6 of the oil leakage detectorof the present invention;

FIG. 13 is a schematic view for describing a method for relocating thecoordinates of pixels in the embodiment 6 of the oil leakage detectionmethod of the present invention;

FIG. 14A is a schematic view for describing a method for calculating thenumber of pixel groups located on straight lines in the embodiment 6 ofthe oil leakage detection method of the present invention; and

FIG. 14B is a typical view for describing a method for calculating thenumber of pixel groups located on straight lines in the embodiment 6 ofthe oil leakage detection method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An oil leakage detector and an oil leakage detection method of thepresent invention will hereinafter be described based on illustratedembodiments. Incidentally, the same reference numerals are respectivelyused in the same components in the respective embodiments.

Embodiment 1

An embodiment 1 of an oil leakage detector of the present invention isshown in FIG. 1 together with an intensity-saturation graph.

As shown in the FIG. 1, the oil leakage detector 100 of the presentembodiment is roughly comprised of an ultra-violet light 1 irradiated onan object 7 to be measured, a color camera 2 which photographsfluorescence from the measurement object 7 irradiated with theultra-violet light 1, a control unit 3 which controls the operations ofthe ultra-violet light 1 and the color camera 2, a recording unit 4which records an image of the measurement object 7 photographed by thecolor camera 2, an image processing unit 5 which invokes the image ofthe measurement object 7 recorded in the recording unit 4 to determinean oil leakage, and a display unit 6 which displays a result ofdetermination by the image processing unit 5.

Further, in the present embodiment, the image processing unit 5calculates the values of saturation and intensity of each pixel in thecolor image of the measurement object 7 photographed by the color camera2 and draws an intensity-saturation characteristic line(intensity-saturation graph 9 a) of the saturation expressed in anX-axis and the intensity expressed in a Y-axis. Further, the imageprocessing unit 5 sets an upper limit and a lower limit of intensity ofeach saturation as a threshold value based on an area without oiladhesion on the surface of the object, and determines, based on theintensity-saturation characteristic line, an area corresponding to apixel group where the Y-axis numeric value of an area without oiladhesion on the surface of the measurement object 7 exceeds a thresholdvalue in the direction in which the value is large (that is, where theintensity exceeds the threshold value of the upper limit), or where theY-axis numeric value of the area without oil adhesion on the surface ofthe measurement object 7 falls below a threshold value in the directionin which the value is small (that is, where the intensity falls belowthe threshold value of the lower limit), to be an leakage oil adheredarea.

Specifically, though means for determining the area corresponding to thepixel group in the image processing unit 5 to be the leakage oil adheredarea will be described in detail later, it determines, based on theintensity-saturation characteristic line (intensity-saturation graph 9a), an area corresponding to a pixel group exceeding a threshold valuein the direction in which the numeric value of intensity is large (thatis, where the intensity exceeds the threshold value of the upper limit),to be a leakage oil adhered area where R (Red), G (Green), and B (Blue)of each pixel indicative of the surface of the measurement object 7photographed by the color camera 2 satisfies a condition ofR²+G²−BR−BG>0, or determines, based on the intensity-saturationcharacteristic line, an area corresponding to a pixel group fallingbelow a threshold value in the direction in which the numeric value ofintensity is small (that is, where the intensity falls below thethreshold value of the lower limit), to be a leakage oil adhered areawhere R, G, and B of the area of the measurement object 7 satisfies acondition of R²+G²−BR−BG<0.

Incidentally, the ultra-violet light 1 is a commercially available blacklight. Further, the color camera 2 is capable of outputting image datato the outside and may be, for example, a versatile one such as a colordigital camera or the like which photographs visible light.

The present embodiment and embodiments 2 to 4 to be described below willnext be made about the case where oil leakage detection of insulationoil generally used in an oil-filled transformer is performed by the oilleakage detector of the present invention, while taking as an examplewhere the oil leakage detector of the present invention is applied tothe oil-filled transformer.

A schematic configuration of the oil-filled transformer will first bedescribed using FIGS. 2 and 3.

In the drawings, reference numeral 15 is a tank of the transformer. Amain body of the transformer comprised of an iron core and windings isstored within the tank 15 together with insulation oil. The main body ofthe transformer and a bushing 14 in the tank 15 are connected to eachother. The tank 15 is connected to a radiator 16 through an upper pipe17 a and a bottom pipe 17 b. Pipes on the tank 15 side and pipes on theradiator 16 side are respectively connected by a junction part (flange)18 a of the upper pipe 17 a and a junction part (flange) 18 b of thebottom pipe 17 b.

The oil-filled transformer having such a configuration, which isgenerally used in a power facility, has a structure in which the bushing14, the tank 15, the radiator 16, the upper pipe 17 a and the bottompipe 17 b are filled with the insulation oil. The junction part (flange)18 a of the upper pipe 17 a and the junction part (flange) 18 b of thebottom pipe 17 b are generally respectively fixed with bolts and nutsthrough packings.

The example illustrated in FIGS. 2 and 3 is intended to detect leakageoil from the radiator 16 and the junction part 18 b of the bottom pipe17 b in the oil-filled transformer by using the oil leakage detector ofthe present invention (the ultra-violet light 1 and the color camera 2in the oil leakage detector of the present invention are illustrated inFIGS. 2 and 3). Incidentally, the present invention can be applied evento the oil leakage detection of the whole oil-filled devices and is notlimited to the oil-filled transformer.

In general, when the insulation oil is irradiated with the ultra-violetlight 1, fluorescence is emitted. The black light used as theultra-violet light 1 includes a visible light component of 380 nm ormore in addition to an ultra-violet component. The visible light orvisible light around the measurement object 7 is reflected when appliedonto the surface of the measurement object 7, and the reflected light isphotographed by the color camera 2. The reflection at this time isbasically diffusion reflection except for the case where the surface ofthe measurement object 7 is a mirror surface.

The saturation (S) and intensity (I) of each pixel is calculated by theimage processing unit 5, using the values of R (Red), G (Green), and B(Blue) of each pixel indicative of the surface of the measurement object7 in the image photographed by the color camera 2.

As calculation equations of the saturation (S) and the intensity (I),there are, for example, generally-known equations 1 and 2.

Saturation(S)=√{square root over (R ² +G ² +B ² −GR−BR−GB)}  1

Intensity(I)=⅓R+⅓G+⅓B  2

An intensity-saturation graph 9 a is created with the intensity (I) ofeach pixel as a Y-axis and the saturation (S) thereof as an X-axis.

As shown in the intensity-saturation graph 9 a of FIG. 1, when thereflection of an area 10 without oil adhesion on the surface of themeasurement object 7 is of diffusion reflection, the relationshipbetween the saturation (S) and the intensity (I) follows the followingequation 3:

$\begin{matrix}{I = {{aS} = {\frac{{\frac{1}{3}R_{0}} + {\frac{1}{3}G_{0}} + {\frac{1}{3}B_{0}}}{\sqrt{R_{0}^{2} + G_{0}^{2} + B_{0}^{2} - {G_{0}R_{0}} - {B_{0}R_{0}} - {G_{0}B_{0}}}}S}}} & 3\end{matrix}$

where a is a constant, and R₀, B₀, and G₀ are the values of R, G, and Bat a given area in the area 10 without oil adhesion on the surface ofthe measurement object 7. The surface color of the measurement object 7and incident light irradiated on the measurement object 7 are constant,the saturation (S) and the intensity (I) change while keeping aproportional relation of the equation 3, according to changes inirradiation light of a point on the surface of the measurement object 7and a photographing angle to the color camera 2. This relation isgenerally known.

Further, the value of the intensity (I) varies on the straight line ofthe equation 3 at the same saturation due to the surface roughness ofthe area 10 without oil adhesion on the surface of the measurementobject 7, and ununiformity in spatial distribution of the incidentlight.

When the ultra-violet light 1 is applied to the insulation oil, a bluefluorescence having a center wavelength of 405 nm is emitted. When thevalue of K defined by a following equation 4 using the values R₀, B₀,and G₀ of R, G, and B of the area 10 without oil adhesion on the surfaceof the measurement object 7 is K>0 where only the component of B afteroil adhesion is considered to increase as compared with when no leakageoil is adhered to the leakage oil adhered area 8, the intensity (I) ofthe leakage oil adhered area 8 becomes larger than the straight line ofthe equation 3. When K<0, the intensity (I) of the leakage oil adheredarea 8 becomes smaller than the straight line of the equation 3.

K=R ₀ ² +G ₀ ² −B ₀ R ₀ −B ₀ G ₀  4

The intensity-saturation graph 9 a shown in FIG. 1 shows where K>0. Inthe case of K>0, a threshold value I₁=aS+b is set to a value larger thanthe maximum value of the values of intensity to respective saturations(S) of a pixel group 10A corresponding to the area 10 without oiladhesion on the surface of the measurement object 7 in parallel with thestraight line of the equation 3. A pixel group 8A exceeding from thethreshold value I₁ is determined to be the leakage oil adhered area 8.Since the leakage oil is adhered to the measurement object 7, it isaffected by the reflection of the leakage oil adhered area (pixel group8A), and changes in the values of saturation (S) and intensity (I) areinfluenced by even the film thickness of the oil. Therefore, thereoccurs a case where variations in the saturation (S) and intensity (I)of the pixel group 8A appear.

Incidentally, when K<0, a threshold value I₂=aS+b′ is set to a valuesmaller than the minimum value of the values of intensity to therespective saturations (S) of the pixel group 10A corresponding to thearea 10 without oil adhesion on the surface of the measurement object 7in parallel with the straight line of the equation 3. A pixel group 8Awhich falls below the threshold value I₂ is determined to be the leakageoil adhered area 8.

With the provision of such a present embodiment, it is possible to carryout oil leakage detection high in detection accuracy, which makes itpossible to also detect colorless oil without complicating the device.

Embodiment 2

FIG. 4 shows an object 7 to be measured adopted in an embodiment 2 ofthe oil leakage detector of the present invention. Incidentally, in thepresent embodiment, the same reference numerals are respectivelyattached to the same elements as in the embodiment 1, and thedescription thereof will be omitted. A description will be made aboutonly different parts. Further, since the control unit 3, the recordingunit 4, the image processing unit 5, and the display unit 6 are the sameas those in the embodiment 1 shown in FIG. 1, their description will beomitted.

In the present embodiment, an area 11 without oil adhesion in any caseis set to the surface of the measurement object 7 in advance. The area11 without oil adhesion in any case is prepared, for example, by settinga cover, seal, or the like on the surface of the object to be measured 7and removing them at the oil leakage detecting. As described in theembodiment 1, the saturation and intensity values of each point of thesurface of the measurement object 7 depend on the incident light, thephotographing angle, and the state of the surface of the measurementobject 7, etc. Therefore, the area 11 may preferably be set to thesurface of the measurement object 7 as areas 11 a and 11 b without oiladhesion in any case in plural form at places where they are away fromeach other, or set to a surface area having the area of such a degree asto include the plural areas 11 a and 11 b without oil adhesion in anycase, which are away from each other.

FIG. 5 is a flowchart when the oil leakage detector of the presentembodiment automatically detects a leakage oil adhered area 8. Theoperation of the oil leakage detector of the present embodiment will bedescribed in detail below using FIG. 5.

First, in STEP1, the ultra-violet light 1 is applied to the measurementobject 7. In STEP2, an image A obtained by photographing it with thecolor camera 2 is stored in the recording unit 4. One example of theimage A is illustrated in FIG. 6A.

In STEP3, the ultra-violet light 1 is turned off. In STEP4, the imageprocessing unit 5 calculates the saturation and intensity from R, G, andB of each pixel of the surface area (including leakage oil adhered area8) of the measurement object 7.

In STEP5, the image processing unit 5 invokes the preset area 11 (11 aand 11 b) without oil adhesion in any case and draws a characteristicline I=aS by the least square method, using the saturation and intensityof each pixel corresponding to the area 11 without oil adhesion in anycase. Further, the image processing unit 5 calculates K defined in theequation 4. The characteristic line I=aS is applied even to an area 10without oil adhesion on the surface of another object 7 to be measured.

When K>0 here, a threshold value I₁ determined to be indicative of anoil leakage is invoked from the recording unit 4 in STEP6. In STEP7, anarea corresponding to a pixel group 8A exceeding the threshold value I₁in the direction in which the numeric value of intensity is large fromthe characteristic line I=aS, is determined to be the leakage oiladhered area 8. As shown hatched in FIG. 6B, a mark is put on the areacorresponding to the image A.

On the other hand, when K<0, a threshold value I₂ determined to beindicative of an oil leakage is invoked from the recording unit 4 inSTEP6′. In STEP7′, an area corresponding to a pixel group 8A which fallsbelow the threshold value I₂ in the direction in which the numeric valueof intensity is small from the characteristic line I=aS, is determinedto be the leakage oil adhered area 8. As shown hatched in FIG. 6B, amark is put on the area corresponding to the image A.

In the present embodiment as described above, an automatic determinationas to an oil leakage and its visualization can be achieved by thesetting of the area 11 without oil adhesion in any case in advance andthe use of the intensity threshold values I₁ and I₂ relative to thecharacteristic line I=aS as well as to obtain an effect similar to thatin the embodiment 1.

Embodiment 3

FIG. 7 shows an object 7 to be measured adopted in an embodiment 3 ofthe oil leakage detector of the present invention. Incidentally, in thepresent embodiment, the same reference numerals are respectivelyattached to the same elements as in the embodiment 1, and thedescription thereof will be omitted. Only different parts will bedescribed. Further, since the ultra-violet light 1, the color camera 2,the control unit 3, the recording unit 4, the image processing unit 5,and the display unit 6 are the same as those in the embodiment 1 shownin FIG. 1, their description will be omitted.

As shown in FIG. 7, an area 11 without oil adhesion in any case is setto the surface of the measurement object 7 in advance. It is desirableto set the area 11 to a larger area.

FIG. 8 is a flowchart when the oil leakage detector of the presentembodiment automatically detects a leakage oil adhered area 8. Theoperation of the oil leakage detector of the present embodiment will bedescribed in detail below using FIG. 8. Incidentally, since theoperations from STEP1 to STEP2 are the same as those in the embodiment2, they will be omitted.

As shown in FIG. 8, in STEP3, the irradiation intensity of theultra-violet light 1 applied to the measurement object 7 is changed.With the change in the irradiation intensity of the ultra-violet lightapplied to the measurement object 7, changes in the saturation andintensity values due to changes in irradiation light of the point on thesurface of the measurement object 7 described in the embodiment 1 andphotographing angle relative to the color camera 2 are simulated.

An image B obtained by photography with the color camera 2 is stored inthe recording unit 4 in STEP4. In STEP5, the saturation and intensityare calculated from R, G, and B of each pixel corresponding to thesurface area (including leakage oil adhered area 8) of the measurementobject 7 in each of the images A and B.

In STEP6, the preset area 11 without oil adhesion in any case is invokedfrom the recording unit, and the values of saturation and intensity ofthe area 11 without oil adhesion in any case, which are obtained fromthe images A and B are utilized to thereby draw a characteristic lineI=aS. Further, K defined in the equation 4 is calculated. In STEP7, thecharacteristic line I=aS obtained in STEP6 is applied to the image A.

When K>0 here, a threshold value I₁ determined to be indicative of anoil leakage is invoked from the recording unit 4 in STEP8. In STEP9, anarea corresponding to a pixel group 8A exceeding the threshold value I₁in the direction in which the numeric value of intensity is large fromthe characteristic line I=aS, is determined to be the leakage oiladhered area 8. As shown hatched in FIG. 6B, a mark is put on the areacorresponding to the image A.

On the other hand, when K<0, a threshold value I₂ determined to beindicative of an oil leakage is invoked from the recording unit 4 inSTEP8′. In STEP9′, an area corresponding to a pixel group 8A which fallsbelow the threshold value I₂ in the direction in which the numeric valueof intensity is small from the characteristic line I=aS, is determinedto be the leakage oil adhered area 8. As shown hatched in FIG. 6B, amark is put on the area corresponding to the image A.

In the present embodiment as described above, it is possible to improvediagnostic accuracy by determining the characteristic line I=aS usingthe saturation and intensity obtained where the different irradiationintensities are used with respect to the area 11 without oil adhesion inany case, as well as to obtain an effect similar to that in theembodiment 1.

Embodiment 4

FIG. 9 is a flowchart for describing an oil leakage detecting operationin an embodiment 4 of the oil leakage detector of the present invention.Here, the same reference numerals are respectively attached to the sameelements as in the embodiments 1 to 3, and the description thereof willbe omitted. Only different parts will be described. Incidentally, sincethe operations other than in STEP5 are the same as in the embodiment 2,they will be omitted.

In the present embodiment illustrated in the drawing, when K>0, n piecesof intensity values corresponding to respective saturations are averagedfrom the minimum value in STEP5. A characteristic line I=aS is drawnfrom the so-obtained average value by the least square method. N>20 ispreferred in order to enhance the accuracy of the saturation-intensitycharacteristic line I=aS of the area 10 without oil adhesion on thesurface of the measurement object 7.

On the other hand, when K<0, n pieces of intensity values correspondingto respective saturations are averaged from the maximum value in STEP5.A characteristic line I=aS is drawn from the so-obtained average valueby the least square method. N>20 is preferred in order to enhance theaccuracy of the saturation-intensity characteristic line I=aS of thearea 10 without oil adhesion on the surface of the measurement object 7.

In the present embodiment as described above, it is possible tocalculate the characteristic line I=aS without providing the area 11without oil adhesion in any case and achieve the simplification of aprocess as well as to obtain an effect similar to that in the embodiment1.

Embodiment 5

FIG. 10 shows an intensity-saturation graph 9 b for oil leakagedetection in an embodiment 5 of the oil leakage detector of the presentinvention. The intensity-saturation graph 9 b shown in the drawing showswhere K>0. Incidentally, here, the same reference numerals arerespectively attached to the same elements as those in the embodiments 1to 4, and the description thereof will be omitted. Only different partswill be described.

Although it has been described in the embodiments 1 to 4 that when thereflection of the area 10 without oil adhesion on the surface of themeasurement object 7 is of diffusion reflection, the relationshipbetween the saturation (S) and the intensity (I) ideally yields I=aS,the straight line does not actually necessarily pass through the originof the intensity-saturation graph 9 b due to the influence of thesurface state of the measurement object 7 and the like. That is, thereis a case where b₀≠0 is reached under I₃=aS+b₀.

In such a case, i.e., when K>0, the threshold value is set toI₄=aS+b₀+b. Further, when K<0, the threshold value is set toI₅=aS+b₀+b′.

In such a present embodiment, it is possible to perform oil leakagedetection by setting the threshold value to I₄=aS+b₀+b when the straightline does not actually necessarily pass through the origin of theintensity-saturation graph 9 b due to the influence of the surface stateof the measurement object 7 and the like, i.e., when K>0, and settingthe threshold value to I₅=aS+b₀+b′ when K<0, as well as to obtain aneffect similar to that in the embodiment 1.

Embodiment 6

FIG. 11 is a flowchart for describing an oil leakage detecting operationin an embodiment 6 of the oil leakage detector of the present invention.

In the present embodiment, the same reference numerals are respectivelyattached to the same elements as those in the embodiments 1 to 5, andthe description thereof will be omitted. Only different parts will bedescribed. Further, since the control unit 3, the recording unit 4, theimage processing unit 5, and the display unit 6 are the same as those inthe embodiment 1 shown in FIG. 1, their description will be omitted. Anintensity-saturation graph 9 c illustrated in FIG. 12 shows where K>0.Incidentally, since the operations from STEP1 to STEP3 are the same asthose in the embodiments 2 and 4, they will be omitted.

As shown in FIG. 11, in STEP4, the image processing unit 5 calculatesthe saturation and intensity from R, G, and B of each pixel of thesurface area (including leakage oil adhered area 8) of the measurementobject 7. Further, the image processing unit 5 calculates K defined inthe equation 4.

Further, in STEP5, the coordinates of each pixel group are relocated.This relocating method is shown in FIG. 13.

As shown in the drawing, the minimum interval of each of the intensityand saturation values is defined, and an intensity-saturation space isdivided in a grid shape. Each pixel is relocated to the closest gridpoint. For example, a pixel 19 is relocated to a grid point 19 a, and apixel 20 is relocated to a grid point 20 a.

When K>0 here, a pixel group obtained by selecting a pixel having theminimum value of the intensity values corresponding to the respectivesaturations is represented as PG1 in STEP6.

On the other hand, when K<0, a pixel group obtained by selecting a pixelhaving the maximum value of the intensity values corresponding to therespective saturations is represented as PG2 in STEP6′.

When K>0 here, in STEP7, two pixels P_(a) and P_(b) are selected pluraltimes at random with respect to the pixel group PG1 to create aplurality of straight line groups L₁ to L_(m).

On the other hand, when K<0, in STEP7′, two pixels P_(c) and P_(d) areselected plural times at random with respect to the pixel group PG2 tocreate a plurality of straight line groups L₁ to L.

When K>0 here, in STEP8, the numbers of pixels lying on the straightlines of the plural straight line groups L₁ to L_(m) created in STEP7are calculated. The number of pixels lying on the straight line of thestraight line group L_(m) is represented as N_(m).

As a method for calculating the above-described pixel number N_(m), thedistances between all pixels of the pixel group PG1 and each of thestraight line groups L₁ to L_(m) are calculated as shown in FIG. 14A.Then, a straight line shortest in distance is selected and counted aspixels lying on the straight line. For example, a pixel 21 and a pixel22 are counted as the pixels lying on the straight line group L₁, and apixel 23 is counted as the pixel lying on the straight line group L₂.

Further, the inclinations of the respective straight lines arecalculated. The inclination of the straight line group L_(m) isrepresented as a_(m).

On the other hand, when K<0, in STEP8′, the numbers of pixels lying onthe straight lines of the plural straight line groups L₁ to L_(n)created in STEP7′ are calculated. The number of pixels lying on thestraight line of the straight line group L_(n) is represented as N_(n).

As a method for calculating the above-described pixel number N_(n), thedistances between all pixels of the pixel group PG2 and each of thestraight line groups L₁ to L_(n) are calculated as shown in FIG. 14B.Then, a straight line shortest in distance is selected and counted aspixels lying on the straight line. For example, a pixel 24 and a pixel25 are counted as the pixels lying on the straight line group L₃, and apixel 26 is counted as the pixel lying on the straight line group L₄.

Further, the inclinations of the respective straight lines arecalculated. The inclination of the straight line group L_(n) isrepresented as a_(n).

When K>0 here, a straight line having a maximum pixel number N_(mmax) isselected in STEP9. When the number of straight lines having the maximumpixel number is plural, a straight line minimum in inclination isselected. This straight line is assumed to be L_(α).

On the other hand, when K<0, a straight line having a maximum pixelnumber N_(nmax) is selected in STEP9′. When the number of straight lineshaving the maximum pixel number is plural, a straight line maximum ininclination is selected. This straight line is assumed to be L_(β).

In STEPS10 and 10′, a distribution range d of the values of intensity(I) on the surface of the measurement object 7 where the oil leakage isdetermined to be absent in advance is read from the recording unitregardless of K>0 or K<0.

Since the distribution range d of the intensity values to eachsaturation value is not necessarily constant, the distribution range dis given by, for example, taking the average value of distributionranges of intensity values to all saturation values or taking themaximum distribution range excepting an abnormal width.

When K>0 here, in STEP11, a pixel group within a distance d is selectedaway from the straight line L_(α) in the directions in which the valueof intensity is large and small, with the straight line L_(α) obtainedin STEP9 as the reference. A straight line I₆ which fits most theselected pixel group is determined. As one example of a fitting method,there is mentioned a method of least square. The so-obtained straightline I₆ is considered to be the characteristic straight line of the area10 without oil adhesion on the surface of the measurement object 7. Thestraight line I₆ does not always pass the origin of theintensity-saturation graph 9 c depending to the surface state of thestraight line I₆.

On the other hand, when K<0, in STEP11′, a pixel group within a distanced is selected away from the straight line L_(β) in the directions inwhich the value of intensity is large and small, with the straight lineL_(β) obtained in STEP9′ as the reference. A straight line I₇ which fitsmost the selected pixel group is determined. As one example of a fittingmethod, there is mentioned a method of least square. The so-obtainedstraight line I₇ is considered to be the characteristic straight line ofthe area 10 without oil adhesion on the surface of the measurementobject 7. The straight line I₇ does not always pass the origin of theintensity-saturation graph 9 c depending to the surface state of thestraight line I₇.

When K>0 here, in STEP12, a threshold value I₈ is created in parallelwith the straight line I₆ at a place a constant distance D in thedirection in which the value of intensity is large apart from thestraight line I₆ obtained in STEP11. As one example of the magnitude ofthe distance D, the distance D is assumed to D=d/2, for example.

On the other hand, when K<0, in STEP12′, a threshold value I₉ is createdin parallel with the straight line I₇ at a place a constant distance Din the direction in which the value of intensity is small apart from thestraight line I₇ obtained in STEP11′. As one example of the magnitude ofthe distance D, there is D=d/2, for example.

When K>0 here, in STEP13, a pixel group 8A exceeding the threshold valueI₈ created in STEP12 in the direction in which the value of intensity islarge, is determined to be indicative of an oil leakage.

On the other hand, when K<0, in STEP13′, a pixel group 8A falling belowthe threshold value I₉ created in STEP12′ in the direction in which thevalue of intensity is small, is determined to be indicative of an oilleakage.

With the provision of such a present embodiment, it is possible to,without complicating the device, automatically set a threshold value fordetermining an oil leakage and automatically detect an oil leakage withhigh accuracy and high sensitivity.

Incidentally, the present invention is not limited to the aboveembodiments and includes various modifications. The above embodimentsare those described so as to facilitate the understanding of the presentinvention and are not necessarily limited to those provided with all thedescribed configurations. Further, it is also possible to replace partof the configuration of an embodiment with the configuration of anotherembodiment. The configuration of another embodiment can also be added tothe configuration of the embodiment. Furthermore, the addition, deletionand replacement of another configuration can also be performed on partof the configuration of each embodiment.

DESCRIPTION OF REFERENCE SIGNS

-   -   1 . . . ultra-violet light, 2 . . . color camera, 3 . . .        control unit, 4 . . . recording unit, 5 . . . image processing        unit, 6 . . . display unit, 7 . . . object to be measured, 8 . .        . leakage oil adhered area, 8A, 10A . . . pixel group, 9 a, 9 b,        9 c . . . intensity-saturation graph, 10 . . . area without oil        adhesion on the surface of measurement object, 11, 11 a, 11 b .        . . area without oil adhesion in any case, 14 . . . bushing, 15        . . . tank of transformer, 16 . . . radiator, 17 a . . . upper        pipe, 17 b . . . bottom pipe, 18 a, 18 b . . . junction part        (flange), 19, 19 a, 20, 20 a, 21, 22, 23, 24, 25, 26 . . .        pixel, 100 . . . oil leakage detector.

What is claimed is:
 1. An oil leakage detector comprising: anultra-violet light irradiated on an object to be measured; a colorcamera which photographs fluorescence from the object irradiated withthe ultra-violet light; a processing unit which determines an oilleakage by the image of the object photographed by the color camera; anda display unit which displays a result of determination by theprocessing unit, wherein the processing unit calculates the values ofsaturation and intensity of each pixel in the color image photographedby the color camera and determines the oil leakage adhered area by thevalues of saturation and intensity of each pixel based on values ofsaturation and intensity of an area without oil adhesion on a surface ofthe object, the values of saturation and intensity of an area withoutoil adhesion on the surface of the object being obtained in advance. 2.The oil leakage detector according to claim 1, wherein means fordetermining the area corresponding to the pixel group to be the oilleakage adhered area in the processing unit draws anintensity-saturation characteristic line of the saturation expressed inan X-axis and the intensity expressed in a Y-axis and determines, basedon the intensity-saturation characteristic line, an area correspondingto a pixel group exceeding the threshold value of the upper limit ofintensity, to be an oil leakage adhered area where R (Red), G (Green),and B (Blue) of each pixel indicative of the surface of the objectphotographed by the color camera satisfies a condition of R2+G2−BR−BG>0,or determines, based on the intensity-saturation characteristic line, anarea corresponding to a pixel group falling below the threshold value ofthe lower limit of intensity, to be an oil leakage adhered area wherethe R, G, and B of the area of the object satisfies a condition ofR2+G2−BR−BG<0.
 3. The oil leakage detector according to claim 1, whereinthe processing unit draws the intensity-saturation characteristic lineof the X-axis saturation and the Y-axis intensity by utilizing the areawithout oil adhesion on the surface of the object.
 4. The oil leakagedetector according to claim 1, wherein the processing unit draws theintensity-saturation characteristic line of the X-axis saturation andthe Y-axis intensity by utilizing the values of saturation and intensityobtained when the ultra-violet light irradiates the area without oiladhesion on the surface of the object with light having differentintensities.
 5. The oil leakage detector according to claim 2, whereinthe processing unit averages small values of intensity corresponding toeach saturation where the R, G, and B of each pixel indicative of thesurface of the object photographed by the color camera satisfies thecondition of R2+G2−BR−BG>0, or averages large values of intensitycorresponding to each saturation where the R, G, and B of each pixelindicative of the surface of the object photographed by the color camerasatisfies the condition of R2+G2−BR−BG<0, and draws theintensity-saturation characteristic line of the X-axis saturation andthe Y-axis intensity by using the average value of those.
 6. The oilleakage detector according to claim 3, wherein the setting of the areawithout oil adhesion on the surface of the object in the processing unitcomprises setting a plurality of areas away from each other or settingan area having an area of such a degree as to include the areas awayfrom each other.
 7. The oil leakage detector according to claim 2,wherein the area corresponding to the pixel group determined to be theoil leakage adhered area in the color image of the object is marked. 8.An oil leakage detection method comprising the steps of, when an oilleakage adhered area of an object to be measured is detected by an oilleakage detector including an ultra-violet light irradiated on theobject, a color camera which photographs fluorescence from the objectirradiated with the ultra-violet light, a processing unit whichdetermines an oil leakage by the image of the object photographed by thecolor camera and a display unit which displays a result of determinationby the processing unit: calculating by the processing unit, the valuesof saturation and intensity of each pixel in the color imagephotographed by the color camera for photographing the fluorescence fromthe object irradiated with the ultra-violet light; determining the oilleakage adhered area by the values of saturation and intensity of eachpixel based on values of saturation and intensity of an area without oiladhesion on a surface of the object, the values of saturation andintensity of an area without oil adhesion on the surface of the objectbeing obtained in advance.
 9. The oil leakage detection method accordingto claim 8, wherein the determination of the area corresponding to thepixel group to be the oil leakage adhered area by the processing unitcomprises drawing an intensity-saturation characteristic line of thesaturation expressed in an X-axis and the intensity expressed in aY-axis and determining, based on the intensity-saturation characteristicline, an area corresponding to a pixel group exceeding the thresholdvalue of the upper limit of intensity, to be an oil leakage adhered areawhere R (Red), G (Green), and B (Blue) of each pixel indicative of thesurface of the object photographed by the color camera satisfies acondition of R2+G2−BR−BG>0, or determining, based on theintensity-saturation characteristic line, an area corresponding to apixel group falling below the threshold value of the lower limit ofintensity, to be an oil leakage adhered area where the R, G, and B ofthe area of the object satisfies a condition of R2+G2−BR−BG<0.
 10. Theoil leakage detection method according to claim 8, comprising the stepof drawing the intensity-saturation characteristic line of the X-axissaturation and the Y-axis intensity using the area without oil adhesionto the object.
 11. The oil leakage detection method according to claim8, comprising the step of drawing the intensity-saturationcharacteristic line of the X-axis saturation and the Y-axis intensity byutilizing the values of saturation and intensity obtained when theultra-violet light irradiates the area without oil adhesion to theobject with light having different intensities.
 12. The oil leakagedetection method according to claim 9, comprising the steps of averagingsmall values of intensity corresponding to each saturation where the R,G, and B of each pixel indicative of the surface of the objectphotographed by the color camera satisfies the condition ofR2+G2−BR−BG>0, or averaging large values of intensity corresponding toeach saturation where the R, G, and B of each pixel indicative of thesurface of the object photographed by the color camera satisfies thecondition of R2+G2−BR−BG<0, and drawing the saturation-intensitycharacteristic line of the X-axis saturation and the Y-axis intensity byusing the average value of those.
 13. The oil leakage detection methodaccording to claim 10, wherein the setting of the area without oiladhesion to the object in the processing unit comprises setting aplurality of areas away from each other or setting an area having anarea of such a degree as to include the areas away from each other. 14.The oil leakage detection method according to claim 9, comprising thestep of marking the area in the color image corresponding to the pixelgroup determined to be the oil leakage adhered area of the object. 15.The oil leakage detection method according to claim 8, comprising thesteps of: by the intensity-saturation characteristic line of the X-axissaturation and the Y-axis intensity, selecting the minimum value of theintensity values corresponding to the respective saturations, utilizinga pixel group obtained by the selection and a distribution range of theintensity values on the surface of the object, obtained in advance whereleakage oil is not adhered, and drawing a characteristic line of asurface area without the oil adhesion, and further creating a thresholdvalue line in parallel with the characteristic line at a place aconstant distance in a direction in which the intensity value is largeapart from the characteristic line, and determining an areacorresponding to the pixel group lying in a direction in which theintensity value is large from threshold value line, to be an oil leakageadhered area; or by the intensity-saturation characteristic line,selecting the maximum value of the intensity values corresponding to therespective saturations, utilizing a pixel group obtained by theselection and a distribution range of the intensity values by thesurface of the object, obtained in advance where leakage oil is notadhered, and drawing a characteristic line of a surface area without oiladhesion, and further creating the threshold value line in parallel withthe characteristic line at a place a constant distance in a direction inwhich the intensity value is small apart from the characteristic line,and determining an area corresponding to the pixel group lying in adirection in which the intensity value is small from threshold valueline, to be an oil leakage adhered area.
 16. The oil leakage detectionmethod according to claim 15, comprising the steps of selecting theminimum or maximum value of the intensity values, selecting two pixelsplural times at random with respect to a pixel group obtained by theselection to create a plurality of straight line groups, and creating astraight line having the maximum value of a number including theselected pixels, and the minimum or maximum value of an inclination. 17.The oil leakage detection method according to claim 16, wherein theselection of the minimum value of the intensity values comprisesdefining the minimum interval of each axis for intensity and saturationwith respect to coordinates of each pixel group, dividing anintensity-saturation graph, and relocating each pixel using a redefinedcoordinate to select a pixel after redefinition of the coordinate. 18.The oil leakage detection method according to claim 16, wherein thecalculation of the number of pixels when the straight line having themaximum value of the number including the selected pixels is selected,comprises calculating distances between all the pixels in the selectedpixel group and respective straight lines therefor to thereby select thestraight line shortest in distance, and calculating each pixel on thecorresponding straight line.
 19. The oil leakage detection methodaccording to claim 15, comprising the step of, as the distribution rangeof the intensity values of the area without oil adhesion on the surfaceof the object, utilizing a distribution range obtained in advance whereleakage oil is not adhered to the surface of the object.
 20. An imageprocessing unit, wherein the image processing unit receives a colorimage photographed by a color camera which photographs fluorescence froman object to be measured irradiated with an ultra-violet light,calculates values of saturation and intensity of each pixel in the colorimage and determines an oil leakage adhered area by the values ofsaturation and intensity of each pixel based on the values of saturationand intensity of an area without oil adhesion on a surface of theobject, the values of saturation and intensity of an area without oiladhesion on the surface of the object being obtained in advance.